Glass fiber strand is typically formed by attenuating filaments through bushing tips located at the bottom of a heated glass fiber forming bushing containing molten glass. As the filaments are attenuated a binder and/or size is applied to them. The filaments are then gathered into one or more unified strands in a gathering shoe, which is typically a grooved wheel or cylinder formed of a material such as graphite. The strand or strands may then be collected on a rotating collet as a forming package, with the strand or strands being traversed across the face of the collet by means of a rotating spiral or traversing guide eye. In other applications, the strand or strands may be passed to a chopper and chopped into particulate strands, collected in a container after attenuation by means of a belt or wheel attenuator, or collected on a moving surface, for example, as a continuous strand mat.
In any glass fiber forming operation, control of the environment in the fiber forming region below the bushing is extremely important. Variations in either temperature or airflow in this region can lead to non-uniform filament diameters and thus to low quality strands. If the variations in either temperature or airflow are severe enough, the filaments may break, requiring a stoppage in the desired continuous operation and a reduction in productivity from the bushing.
Several means have been attempted in the past to control the environment below the bushing. A pair of blowers have been employed below the bushing to both attenuate the filaments from the bushing and aspirate air downwardly with filament flow. U.S. Pat. Nos. 2,234,986; 3,021,558; 3,532,479; 3,547,610; 3,836,346 and 3,881,903 describe such operations. In another operation, described in U.S. Pat. No. 3,969,099, an air stream is passed to the region directly below the bushing from a blower which diverts and irregularly deflects the air stream prior to its release to the bushing region. There is no illustration in this patent of aspirating any additional air from the environment around the bushing into the flow from the blower. In U.S. Pat. No. 4,033,731, a different air blower is disclosed including a plurality of fins for separating various sections of air from a header to produce an even air stream across the width of the bushing. In this patent, the airflow is in a generally vertical direction to both cool the region below the bushing and control the environment therein.
While such methods and apparatus have been successful to control the environment below the bushing, the methods and apparatus previously employed have consumed a great amount of high pressure air or other gaseous cooling fluid. It is desirable, therefore, to control the environment below the bushing while reducing substantially the consumption of compressed air or other gaseous cooling fluid necessary to give airflows sufficient to control the environment below the bushing.